Art of treating cast iron



-Patented Oct. 7, 1924' UNITED STATES SAMUEL B. PACK, OF WASHINGTON, DISTRICT OF GOLUMBTA.

ART or TREATING CAST Inc-n.

No Drawing. Application filed October 28, 1916, Serial 1T0. 128,258. Renewed March 8, 1924.

To all whom it may comem.

Be it known that I SAMUEL B. PACK, a citizen of the United States, residing at Washington, District of Columbia, have invented certain new and useful Improvements in the Art of Treating CastvIron, of which the following is a specification.

It is a well known fact that if cast iron be heated to atemperature at which the metal shows color, and then allowed 'to cool, it becomes permanently expanded; and that this expansion may be increased, within limits, by repeatedly heating the metal to the required degree and allowing it to coolthis phenomenon being sometimes referred to as the growth of cast iron. Until recently, so far. as I am aware, this characteristic of cast iron has never been utilized, and

indeed was considered a necessary objection incident to the use of this metal where sub-' jected to great heat. But of late it has been discovered that the property of cast iron to'become permanently expanded has been utilized, particularly in the expansion of the pistons of internal combustion engines. In the industrial application of this property of cast iron, it sometimes becomes desirable to-expand it very considerably; my present invention relates more especially to the treatment of the metal to secure such larger expansion, having for one of its objects to so treat the metal as to secure a rapid growth thereof by separate enlargements that are caused to quickly succeed.

each other until the desired size and condi tion of the metal is attained. It has also for its objectto utilize this characteristic of cast iron in the making of novel products,

of which expanded cast iron is an ingredient, and in the process of making such products.

Heretofore, in the treatment of cast iron to permanently expand it, it .has been considered necessary by certain experimentors and operators, to maintain the metal for a considerable length oftime at the temperature to which it must be raised to secure a permanent expansion. But I have discovered that this necessity does not exist. it being sufiicient if the metal be brought to .the desired temperature and then immediately cooled, or partially cooled, the permanent expansion taking place apparently coincidentally with the attainment of the desired temperature throughout the body of metal. It has also been considered necesand.

in the expenditure of heat energy, especially where the number of successive heatings in order to attain the desired degree of expansion, is considerable.

I have discovered that the desired results may be attained if between heatings the metal being treated be only partially cooled, instead of entirely cooled or brought to the temperature of the atmosphere; and that cast iron may be permanently and rapidly expanded to a very considerable degree by heating it to or beyond a temperature at which permanent expansion takes place, for example, to a red heat, and then immediately partially cooling it, as for instance, until it loses its color, but not to a temperature approximating that of the atmosphere, and then again raising its temperature from this partially cooled state until it again shows color, and alternately repeating these heating and partially cooling steps until the desired degree of enlargement has been socured. Thus, if the article is being increased in size by small increments of enlargement, I heat it to a cherry red, then reduce its temperature until the metal loses its color, then immediately again heat it to a cherry red, and so on, alternating heatings and partial coolings, between the limits indi-' ca ted. until the desired amount of expansion has taken place. If it be desired to more rapidly increase the size of the article, by greater increments of growth or enlargement, I heat the metal to a higher degree, even to a white heat. and then partially cool it between heatings. The partial cooling may be carried to the extent of causing the metal to become dull red. or even, to entirely lose its color. The higher temperatures just referred to may be utilized where the article treated is of a character in which distortion is not likely to occur, or where it is unimportant whether it takes place or not; while the lower temperatures above indicated will be employed where more accurate results are to be attained and the danger of distortion is to be avoided.

The best. results, in general, are obtained by bringing the metal to a temperature from 1400 degrees F. to 1500 degrees F., and then immediately cooling it until all color disappears in the metal, and repeating these steps until the desired expansion has been attained. The heating ma be effected in an ordinary furnace, the nished or supplied either directly from the combustion fuel, by electricity, or by superheated steam; while the cooling may be secured by shutting off the supply of heat either automatically, or manually, upon the article attaining the desired temperature, without removing it from the furnace; or the cooling may be hastened by exposing the heated metal to the open air or to. a blast of cooling air, without injury either to the article or to the working of the process. These are details of operation falling within the scope of my invention broadly considered.

I have been able, by the method of treatment described, to secure in a comparatively short space of time, an enlargement or growth of cast iron, of very considerable extent beyond its original size.-

It is found that the increase in the volume of the metal, as might be expected, is attended by a reduction in specific gravity; and this fact may be taken advantage of where lightness is desirable, as for instance in the manufacture of pistons for internal combustion engines, for by this process,cast iron istons that are of considerabl less speci c ravity than those now in vogue may be guic y and cheaply manufactured by casting them smaller in size than they are to be when finished, then enlarging the castings by the permanent expanding process herein described to the desired size, and finishing them by grinding or machining as may be required. For many purposes the method of treatment thus far described will be sufiicient in itself, whether exercised for the purpose of reducing the specific gravity of the metal by increasing the dimensions of new castings beyond the foundry sizes. or for the enlargement of used and worn castings in order to restore them to working size or to over size, in order that they may be reshaped.

My ex riments and observations have led me to be ieve that the permanent expansion of cast iron articles up to a certain degree does not preceptibly impair the strength and other desirable characteristics ofthe metal, and indeed I have been led t6 believe that the metal is improved by such treatment. But when the expansion becomes large, the metal becomes appreciably more porous and loses somewhat in strength. I have utilized this incident porosity of the metal, due to large expansion, in roducing certain new metal ducts in which the permanently expande cast iron constitutes the principal part. These products possess characteristics different in one respect or another from those of the cast iron itself, as for instance, they may be much more resistive than cast 1ron to oxidation or corrosion incident to eat being fur where it i allowed contact with the atmosphere, gases, or liquids, or'they may take on the appearance, and more or less the characteristics, of other metals.

In operating according to this part of my invention, I impregnate the expanded, porous cast iron with a material, which when in a fluid state will enter the pores of the iron. This I accomplish by immersing the expanded cast iron, from which any surfacescale has, preferabl been removed, in a heated fluid bath 0 the desired material,

to remain until the desired degree of impregnation has taken place.

Among the specific applications of this part of m invention, I may refer to the following: il'here piping for conducting liquids or gases that are not under much pressure is to be produced, I may take ordinary cast iron pipe and permanently expand it, increasing it both in length and diameter, and then immersing this expanded pipe in a heated bath of tar, bitumen, or similar substance, which when sufiiciently heated will enter the ores of the metal ofthe pipe, rendering it i hly resistive to corrosive action and less lia le to leakage.

Another and more general application of the invention is the impregating of the expanded cast iron by other metals, such as copper, aluminium or brass. These add strength to the article or product and give to it many of the characteritsics of the impregnating metal employed. To secure impregnation of cast iron by another metal, I immerse the cast iron article preferably when heated to a red heat in a bath of the desired metal and there allow it to remain until the pores of the iron article become filled, more or less, after which it is taken out and allowed to cool. The length of time of immersion depends upon the porosity of the iron article, the thickness of its walls, and the degree of impregnation desired. Thus, in operating upon a cast iron ring which had been reviously expanded from four and one-half to five inches in diameter, the body of the ring being originally three-sixteenths of an inch in thickness, I was able to secure a fair degree of penetration, by immersing it in molten brass for a few minutes only; and the complete penetration of the ring took place in less than thirty minutes. orresponding results have been secured with molten aluminium and molten copper as the impregnating mediums.

The metals which are ordinarily used for impregnating expanded cast iron are such as melt at a lower temperature than does cast iron, and are more highly resistive than cast iron to such gases and liquids asthe articles treated by this process might ordinarily be subjected to.

Cal

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metal that have entered the pores of the.

iron. In this manner a coat of considerable thickness may easily, quickly and cheaply be applied to the cast iron.

One application of this feature of my in:

vention contemplates the. production of stock metal-such as rods, plates, etc., adapted to be carried in stock and sold 'for various urposesby expanding cast iron articles of the desired shapes until they become porous, and then impregnating tiese with a metal that adds strength and durability. to the finished products.

It is well knownthat many articles now made of cast iron, such as stove grates, stove lids, etc., Where subjected to repeated heatings, become war ed and distorted in shape, due, it is believe to perman'eht expansion. In making such articles according to my'invention, the articles or the castings from which they are made, are first heat-expanded until the become porous to an extent beyond which little expansion will take place even if repeatedly heated and cooled, and when thus expanded and porous, treated as described so as to become impregnated with a strength-imparting metal. They are then shaped or finished as may be'required. Such articles retain their shape, are sufficiently strong for the purposes for which they are used, and are more resistive to disintegrating tendencies, such as oxidation, than is ordinary cast iron.

Among other uses to which my inventionmay be put, is the manufacture of composite metal pipe. I take a steel pipe, or other pipe that does not become ermanently expanded by heat treatment, and insert into this a cast iron pipe, and heat-expand the latter until it fits, and is united with the external pipe.

The external pipe may be'used for giving strength to the completed article, orfor appearance sake, or for any other characteristic which it may possess.- The internal cast HOn pipe is employed for cheapness. It may or may not be impregnated with another metal as described. Where the pipe is intended to he a conduit for corrosive liquids or gases it would probably be of advantage to impregnate the cast iron with a metal that resists the attacks of the fluid the pipe is expected to conduct.

A somewhat similar application of my invention to that just described is in the making of car wheels in which the central portion' of the wheel is of cast iron and where theti-re or rim is of steel. Heretofore it has been customary to shrink the tire upon the central body of the wheel, but according to my invention the body is expanded into contact and union with the rim or tire.

I believe that better results can be obtained by my process than by the method just referred to and now in vogue, as a more intimate and more permanent union can thus be secured between the two metals.

The permanent expansion of cast iron, as a preliminary to its treatment with materials or .ingredients for bringing on desired physical and chemical changes, whereby the entrance or action of the ingredients, whether in a solid, fluid, or gaseous state, are

facilitated, by the opening up of the pores.

of the iron, is within the scope of my invention broadly considered. Thus, the exnaceous material; or carbonimthe iron may be readily withdrawn by a similar treatment with an iron oxide. It may be found that impurities commonly present in cast iron and difficult or impossible to remove by known methods can be readily eliminated by expandin the iron to a degree which will make it su ciently porous and then treating it .with the proper re-agent.

I do not, in this case, claim the process in the art of permanently expanding cast iron, herein described, which consists in heating the iron to a temperature at which it takes a permanent expansion, then partially cooling it, and then, from this partially cooled state, again raising its temperature to ,crease in size is attained.

.Having described my invention, what I claim is:

1. The herein described process, in the art of treating cast iron, which consists in permanently heat-expanding the metal until it becomes porous, then impregnating it with .a material that will enter. the pores and render it increasingly resistive to corrosion or oxidation.

2. The herein described process, in the art of treating cast iron, which consists in permanently heat-expanding the metal until it becomes porous, and then immersing such expanded metal in a fluid bath of a material that will enter the pores of the metal, and becoming solid, remain therein.

3. The herein described process, in the art of treating cast iron. which consists in permanently heat-expanding the metal until it becomes porous, and then immersing such expanded metal in a fluid bath of a metal that will enter the pores of the expanded cast iron.

4. The herein described process, in the art of treating cast iron, which consists in permanently heat-expanding the metal until it becomes porous, then immersing it in a fluid bath of a metal that melts at a temperature below the melting point of cast iron, whereby the expanded cast iron becomes impregnated with the other metal.

5. The herein described process, in the art of treating cast iron, which consists in permanently heat-expanding the metal until it becomes porous, then immersing such expanded metal, while red hot, in a molten bath of another metal, whereby the cast iron becomes impregnated with the metal into which it is immersed.

6. The herein described process, in the art of treating cast iron, which consists in subjecting a cast iron object to a series of repeated heat treatments to cause it to become permanently expanded and porous, and then impregnating such permanently heatexpanded object with a material that will enter and fill the pores and which is of a nature to cause the object to be increasingly resistive to corrosion or oxidation.

7. In the art of treating cast iron, the herein described novel product consisting of permanently heat-expanded cast iron, the

minute pores in which, due to the permanent heat-expansion, have been filled with a rust- 'and corrosion-resisting substance.

8. A product such as described in claim 7 in which the material that fills the minute pores of the permanently heat-expanded cast iron is a metal other than iron.

9. A product such as described in claim 8 in which the impregnating metal melts at a lower temperature than does cast iron and is more resistive to corrosion and atmospheric oxidation than is cast iron.

10. In the art of treatin cast iron, the herein described novel prodiict, which consists of permanently heat-expanded cast iron the minute pores in which, caused by the permanent heat-expansion, have been filled with a metal that melts at a lower tempera ture than does cast iron and the surface of which product is coated with the impregnating metal, the coating being intimately united with the cast iron by the particles of the coating and impregnating metal than enter and fill the pores of the cast iron.

SAMUEL B. PACK. 

